The question of what constitutes the “biggest” living thing in the world is complex because size can be defined in multiple ways. The answer changes depending on whether one measures an organism by its total area, its overall mass or volume, or its height. Many of the planet’s largest organisms are not the visible creatures we might expect, but rather vast, hidden networks of life. The true scale of life on Earth often lies beneath the soil or in the deep ocean, challenging our traditional notions of individual size.
The Vastness of the Honey Mushroom
The organism that holds the title for the largest area of continuous spread is the dark-colored honey mushroom, Armillaria ostoyae, located in the Malheur National Forest in eastern Oregon and often nicknamed the “Humongous Fungus.” It is a parasitic species that slowly kills the trees it infects by spreading its root-like structures, called rhizomorphs, through the soil.
Genetic testing has confirmed that this subterranean network is one continuous individual, covering approximately 2,385 acres, or about 3.7 square miles. This massive size is largely invisible, as the mushroom-shaped fruiting bodies that appear above ground are only a small part of the organism. The vast majority of its biomass exists as a web of thread-like filaments known as mycelium.
The Oregon specimen’s immense size is attributed to its age and the dry climate of the region, which limits competition from other fungi and prevents the successful establishment of new, competing colonies from spores. This fungus has been estimated to be around 8,000 years old. Its total physical weight is difficult to measure precisely, but estimates have ranged up to 35,000 tons.
The Massive Clonal Plant Colonies
The concept of size shifts when considering organisms that achieve their mass through cloning, rather than through a single, continuous body like the fungus. The most prominent example is Pando, a grove of Quaking Aspen (Populus tremuloides) located in Utah’s Fishlake National Forest. Pando is genetically a single male organism, consisting of over 40,000 individual tree stems.
Each visible aspen tree in the grove is a genetically identical ramet, or clone, that sprouts from one immense, interconnected root system. This massive root structure spreads across 106 acres, and while the individual stems typically live for only about 130 years, the root system itself has persisted for thousands of years. Estimates of Pando’s age vary widely, with some analyses suggesting it is up to 14,000 years old, and others speculating the root mass could be significantly older.
Pando is commonly cited as the heaviest known living organism, with an estimated total mass of about 6,600 short tons. This measurement is based on the combined weight of the root system and all the above-ground stems.
The Tallest Individual Organisms
A different metric for measuring “biggest” is the sheer volume of a single, non-clonal stem. The Coast Redwood (Sequoia sempervirens) holds the record for the tallest living tree, with the current tallest specimen, named Hyperion, reaching a height of over 380 feet. These trees are slender and optimized for vertical growth, often reaching heights far beyond the largest specimens of other species.
In contrast, the Giant Sequoia (Sequoiadendron giganteum) is the species known for having the greatest volume and mass of any single-stem tree. The most massive individual is the General Sherman tree, located in Sequoia National Park, which stands about 275 feet tall. Its enormous girth gives it a trunk volume of approximately 52,500 cubic feet.
This massive volume makes the General Sherman tree the largest living organism in the world by single-stem volume, though it is shorter than the Coast Redwood. While the General Sherman tree is estimated to weigh nearly 1,400 tons, historically recorded Coast Redwoods, such as the now-fallen Lindsey Creek Tree, may have had a greater total wood volume.
The Largest Mobile Creature
When focusing on the animal kingdom, the title of largest living creature goes to the Blue Whale (Balaenoptera musculus). This marine mammal is the largest animal known to have ever existed, dwarfing even the largest dinosaurs. Blue whales can reach lengths of over 98 feet, and the largest recorded individuals have weighed close to 200 tons.
A blue whale’s heart alone can weigh around 400 pounds, making it the largest heart of any animal. Its tongue can weigh as much as an elephant, and its main artery is large enough for a small human to crawl through. This immense size is supported by a diet consisting almost entirely of tiny krill, consuming up to eight tons of the small crustaceans daily during feeding season.